1. Field of the Invention
This invention relates to an automatic engine stop-restart system capable of automatically stopping or restarting an engine in accordance with the operating conditions of a vehicle.
2. Description of the Prior Art
Some motor vehicles have mounted thereon an automatic engine stop-restart system capable of automatically stopping an engine, and thereafter, restarting the engine by an ordinary starting operation (for example, the depression of a clutch pedal) when the vehicles are stopped at an intersection and the like during running through an urban district. The provision of such a system as described above makes it possible to limit the operation of the engine to the time when necessary, thereby enabling to achieve decreased quantities of exhaust gas and reduced fuel consumption.
Heretofore, there has been adopted a method of cutting the current passage to an igniter by a relay or the like in stopping the engine by the system of the type described. More specifically, the current passage to an ignition system a cut off to prevent an ignition plug from discharging a high voltage, whereby explosions do not occur in combustion chambers of the engine, thus enabling to stop the engine.
However, heretofore, the automatic engine stop-restart system has been arranged only to cut the current passage to the ignition system, thereby allowing the residual fuel being stagnant in a fuel supply system such as a slow-port and the like to enter the engine combustion chambers in the process of reciprocation of pistons due to the inertial force. By this, sometimes explosions occur despite non-operation of the ignition system, thus possibly causing "run-on" of the engine.
Recently, there is a strong indication that not only the automatic stop-restart system but also a plurality of controls such as fuel control, air-fuel ratio control and ignition control are collectively controlled by a microcomputer or the like, and ignition signals (rotational speed data) are required as one of the data. Now, in the analogue type ignition circuit of the piror art, ignition signals have been obtainable until the engine is stopped. However, in the digital type ignition circuit of the recent years, such an arrangement is necessitated to adopt that the power supply to the circuit is cut off simultaneously with the cut-off of the ignition system, whereby the cut-off the ignition system turns the ignition signals OFF. In consequence, there has been presented the disadvantage that the turn-OFF of a key switch causes the ignition signal data to be unobtainable.